Invention relates to an optical coupler.
Couplers of this kind are used in optical communications systems, in particular, for instance in optical fiber amplifiers. These amplifiers are inserted into optical transmission paths and amplify the signal light carried in a transmission line. To enable controlling the light output, it is desirable to measure the input power, output power or pump power of the amplifier, for instance.
Optical fiber amplifiers in which the signal light or pump light is detected at the end of a free branch on the output side of the pump coupler are known from two articles in the Journal of Lightwave Technology, Vol. 9, No. 2, February 1991, pp. 261-265 and pp. 291-296. Depending on the pump coupler used, a strong polarization dependency of the light may occur.
The object of the invention is to provide a coupler made up of optical fibers in a system for monitoring the light carried in the fiber at the coupler output during operation.